The present disclosure generally relates to systems and methods for prediction of gas turbine trips due to component failures such as electro-hydraulic valve (gas control valve) system failures.
Gas Turbines are the main power producing components for combined cycle/independent power plants. A mixture of air and fuel is burnt in the combustor to produce thermal/heat that is converted into mechanical energy in the several stages of the turbine. Since the firing temperature of the combustor is very high (in the range of 1300-2200° F. (704-1204° C.)), the state of the combustor is measured by mounting thermocouples (TC) in the turbine exhaust. A dedicated controller assesses the state of the combustion process from these thermocouples and further determines if there are any abnormal operations in the combustor. If there is any abnormal event, it warrants immediate shut down of the combustor, hence the gas turbine trip initiates, which is a rapid and uncontrolled shutdown of a gas turbine to protect damaging of gas turbine components or the whole system. Fuel/Gas Control Valves (GCV) and Inlet Guide Vanes (IGV) are used to control the amount of fuel and air supplied to the combustors. Electro-hydraulic servo actuators are used to control GCV and IGV, which reside in a closed loop controller circuit. Since system/component failure in the controller circuit can cause damage to the gas turbine, most of the components have some form of indicator to feedback (e.g., Linear Variable Differential Transducer (LVDT)). Their responses to the feedback are received in the controller circuit, allowing corrections or updates. In the control loop, different components of the GCV (like electro-hydraulic servo valve, position indicator and fuel control actuator, etc.) may fail providing an erroneous reading, and the controller tries to balance the error in the closed loop circuit, which can cause damage to the other system. The controller initiates a trip to prevent damage to the turbine. Many existing servo system monitoring and diagnostics do not predict trips due to the aforementioned failures. For example, gas control valve related problems can cause the combustion instability due to improper air to fuel ratio, which will result in gas turbine trip. Similarly GCV related issues may also lead to GCV not tracking trips because controller will trip the turbine when gas control valve command and feedback error is exceeding some threshold value for some time delay. A trip is a rapid uncontrolled shutdown of the gas turbine that is initiated by the turbine controller to protect the turbine from failures. In general, there can be several types of failure modes for a gas control valve system such as mechanical actuator leakages, mechanical jamming, servo issues, filter choking, loose wiring, LVDT failures etc. In many circumstances, operators typically cannot predict trips due to GCV system failures.
Unwarranted trips, as mentioned above, can cause revenue loss and also have the adverse effect of reducing life of turbine components. Hence, there is a need for predicting an impending trip reliably and preventing loss of useful life of a gas turbine.